1. Field
This invention generally relates to the recombinant production of therapeutic proteins. More specifically, the invention is directed to glycosylated interleukin-2 muteins which can selectively activate T cells (PHA-blasts) and reduce activation of Natural Killer (“NK”) cells.
2. Background
The biological activity of a glycoprotein is dependent upon not only the integral structure of the protein, but also the properties of the oligosaccharide covalently attached to the protein. By influencing the physico-chemical and biological properties of proteins, oligosaccharides can modulate the therapeutic effect of a glycoprotein pharmaceutical. It is well recognized that glycosylation can affect solubility, resistance to proteolytic attack and thermal inactivation, quaternary structure, activity, targeting, antigenicity, functional activity, and half-life of the protein. The role of oligosaccharide in determining the in vivo activity of EPO and the half-life of tissue plasminogen activator has been reported.
Proleukin® (interleukin-2) has been approved by the FDA to treat melanoma and renal carcinoma. However, due to the toxic side effects associated with interleukin-2, there is a need for a less toxic IL-2 mutein that allows greater therapeutic use of this interleukin. Although non-glycosylated interleukin-2 has been produced in E. coli with full biological activity, proper refolding of the recovered protein and the potential for altered pharmacokinetics have been areas of concern. It is known that the purification of interleukin-2 derived from E. coli requires the use of chaotropic and toxic agents such as guanidine chloride and urea. Thus it would be advantageous to produce glycosylated IL-2 muteins in mammalian cells where the use of harsh reagents can be avoided.
U.S. Pat. No. 5,417,970 to Roskam et al. (May 23, 1995), incorporated herein by reference, discloses a wild type IL-2 preparation. The above-cited related application of Shanafelt et al. discloses IL-2 muteins and states that the muteins may be expressed in a variety of cells, including microbial, plant, and animal cells, including mammalian cells. We have now found a way to make such IL-2 muteins in glycosylated form from mammalian cells. The characterization and details for making a preferred IL-2 mutein are described below.